feat(slash_cmds): can be functions and modules (#844)

Co-authored-by: Oli Morris <olimorris@users.noreply.github.com>

Author: olimorris

lua/codecompanion/strategies/chat/slash_commands/init.lua

@@ -56,6 +56,11 @@ function SlashCommands:execute(item, chat)
   local label = item.label:sub(1)
   log:debug("Executing slash command: %s", label)
 
+  -- If the user has provided a callback function, use that
+  if type(item.config.callback) == "function" then
+    return item.config.callback(chat)
+  end
+
   local callback = resolve(item.config.callback)
   if not callback then
     return log:error("Slash command not found: %s", label)